Enhanced Multi Channel Alignment

ABSTRACT

A imprint lithography system operable for imprinting a pattern into a material deposited between an imprint mold and a substrate, the system including, inter alia, a first set of imaging units positioned at a first angle relative to normal of the substrate; and a second set of imaging units positioned at a second angle relative to normal of the substrate, wherein the first and second angles are not equal to each other.

This application for patent claims priority to U.S. Provisional Patent Application Ser. Nos. 60/788,809 and 60/788,810, which are hereby incorporated by reference herein.

BACKGROUND INFORMATION

Nano-fabrication involves the fabrication of very small structures, e.g., having features on the order of nanometers or smaller. One area in which nano-fabrication has had a sizeable impact is in the processing of integrated circuits. As the semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, nano-fabrication becomes increasingly important. Nano-fabrication provides greater process control while allowing increased reduction of the minimum feature dimension of the structures formed. Other areas of development in which nano-fabrication has been employed include biotechnology, optical technology, mechanical systems and the like.

An exemplary nano-fabrication technique is commonly referred to as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as United States patent application publication 2004/0065976 filed as U.S. patent application Ser. No. 10/264,960, entitled, “Method and a Mold to Arrange Features on a Substrate to Replicate Features having Minimal Dimensional Variability”; United States patent application publication 2004/0065252 filed as U.S. patent application Ser. No. 10/264,926, entitled “Method of Forming a Layer on a Substrate to Facilitate Fabrication of Metrology Standards”; and U.S. Pat. No. 6,936,194, entitled “Functional Patterning Material for Imprint Lithography Processes,” all of which are assigned to the assignee of the present invention and all of which are incorporated by reference herein.

An imprint lithography technique disclosed in each of the aforementioned United States patent application publications and United States patent includes formation of a relief pattern in a polymerizable layer and transferring a pattern corresponding to the relief pattern into an underlying substrate. The substrate may be positioned upon a motion stage to obtain a desired position to facilitate patterning thereof. To that end, a template is employed spaced-apart from the substrate with a formable liquid present between the template and the substrate. The liquid is solidified to form a solidified layer that has a pattern recorded therein that is conforming to a shape of the surface of the template in contact with the liquid. The template is then separated from the solidified layer such that the template and the substrate are spaced-apart. The substrate and the solidified layer are then subjected to processes to transfer, into the substrate, a relief image that corresponds to the pattern in the solidified layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a simplified side view of a lithographic system having a template spaced-apart from a substrate;

FIG. 2 illustrates an inclined microscope unit having x-y and focusing motions;

FIG. 3 illustrates microscopes with different inclined angles depending on the 1^(st) order angle of the imaging grating;

FIG. 4 illustrates microscope configurations using beam re-directing optics such as prism and mirror;

FIG. 5 illustrates an exemplary 8-channel imaging system with four sets of the microscopes shown in FIG. 3;

FIG. 6 illustrates a 16-channel imaging system using a beam splitter and two sets of the systems shown in FIG. 5;

FIG. 7 illustrates relocated imaging channels corresponding to a change of imprinting field size for a case of partial field imprinting (left lower is being imprinted) where microscopes 1 through 6 are relocated;

FIG. 8A illustrates a top view of a more detailed depiction of system 500;

FIG. 8B illustrates a side view showing more detail of system 500;

FIG. 9 illustrates a more detailed depiction of system 600; and

FIG. 10 illustrates a side view of system 500.

DETAILED DESCRIPTION

Referring to FIG. 1, a system 8 to form a relief pattern on a substrate 12 includes a stage 10 upon which substrate 12 is supported and a template 14, having a patterning surface 18 thereon. In a further embodiment, substrate 12 may be coupled to a substrate chuck (not shown), the substrate chuck (not shown) being any chuck including, but not limited to, vacuum and electromagnetic.

Template 14 and/or mold 16 may be formed from such materials including but not limited to, fused-silica, quartz, silicon, organic polymers, siloxane polymers, borosilicate glass, fluorocarbon polymers, metal, and hardened sapphire. As shown, patterning surface 18 comprises features defined by a plurality of spaced-apart recesses 17 and protrusions 19. However, in a further embodiment, patterning surface 18 may be substantially smooth and/or planar. Patterning surface 18 may define an original pattern that forms the basis of a pattern to be formed on substrate 12.

Template 14 may be coupled to an imprint head 20 to facilitate movement of template 14, and therefore, mold 16. In a further embodiment, template 14 may be coupled to a template chuck (not shown), the template chuck (not shown) being any chuck including, but not limited to, vacuum and electromagnetic. A fluid dispense system 22 is coupled to be selectively placed in fluid communication with substrate 12 so as to deposit polymeric material 24 thereon. It should be understood that polymeric material 24 may be deposited using any known technique, e.g., drop dispense, spin-coating, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), and the like.

A source 26 of energy 28 is coupled to direct energy 28 along a path 30. Imprint head 20 and stage 10 are configured to arrange mold 16 and substrate 12, respectively, to be in superimposition and disposed in path 30. Either imprint head 20, stage 10, or both vary a distance between mold 16 and substrate 12 to define a desired volume therebetween that is filled by polymeric material 24.

Referring to FIG. 1 typically, polymeric material 24 is disposed upon substrate 12 before the desired volume is defined between mold 16 and substrate 12. However, polymeric material 24 may fill the volume after the desired volume has been obtained. After the desired volume is filled with polymeric material 24, source 26 produces energy 28, e.g., broadband energy that causes polymeric material 24 to solidify and/or cross-link conforming to the shape of a surface 25 of substrate 12 and patterning surface 18, defining a patterned layer 50 on substrate 12.

The broadband energy may comprise an actinic component including, but not limited to, ultraviolet wavelengths, thermal energy, electromagnetic energy, visible light and the like. The actinic component employed is known to one skilled in the art and typically depends on the material from which imprinting layer 12 is formed. Control of this process is regulated by a processor 32 that is in data communication with stage 10, imprint head 20, fluid dispense system 22, source 26, operating on a computer readable program stored in memory 34.

Embodiments of the present invention are an enhancement of a previously disclosed system described in U.S. patent application Ser. No. 11/000,331 entitled “Interferometric Analysis for the Manufacture of Nano-Scale Devices,” which is incorporated herein by reference in its entirety, referred to as the iMAT system. The embodiments have the following advantages:

1. More microscopes (i.e., >6) and hence more data points are measured; and

2. Fully automated for all absolute positioning. (A unique feedback scheme is also explained for field size reconfiguration.)

FIG. 2 illustrates an inclined microscope unit 200 that can capture the alignment mark images without blocking the UV beam path. This imaging unit 200 is attached on an absolute positioning X-Y stage 201 and it has a focusing automation. Such an absolute X-Y positioning is necessary to relocate each microscope 200 according to the field size or the location of the alignment marks. On practical embodiment is to use a set of small motion range linear sliders that are coupled with actuators and LVDTs (Linear Variable Differential Transformers). Other proposed feedback devices are potentiometers and laser distance measuring sensors, etc.

Precise imprinting requires alignment systems that align the imprint mold in precise alignment with the substrate (wafer) and portions thereof. Multiple imaging systems are utilized to align with marks on the substrate.

When it is necessary to fit multiple microscope units so that multiple alignment marks can be imaged, mechanical interference must be handled carefully. As presented in a previous application (U.S. patent application Ser. No. 11/000,331 entitled “Interferometric Analysis for the Manufacture of Nano-Scale Devices”), alignment measurement systems in this invention do not use a large NA (Numerical Aperture) microscope. However, the relative small field sizes where multiple alignment marks are positioned make the microscope configuration task very difficult even with low NA (<0.1) microscopes. If the imprint field size is 26 mm by 33 mm, it may be necessary to position two imaging units next to each other where their beam paths are spaced by less than 26 mm. Further, if the two alignment marks are closer to each other, the space between their corresponding imaging units needs to be smaller too. In order to overcome the limited space problems, alternative microscope configurations are herein disclosed.

FIG. 3 illustrates two microscope units 200 with different inclined angles (8 degrees and 16 degrees). By altering the inclined angles, it is possible to bring their focusing points much closer as compared to the case of the same inclined angle configuration. Inclined angles are mainly governed by the grating pitch. As shown, microscope 200 at the 8 degree pitch aligns to alignment mark 302 on substrate 301, while microscope 200 at the 16 degree pitch aligns to alignment mark 303. Microscope inclined angles are corresponding to the 1^(st) or 2^(nd) diffracting angles of the alignment make gratings.

Referring to FIGS. 4A and 4B, there are illustrated two alternative microscope configurations utilizing microscope 200 with either beam offset optics (prism) 401 or mirrors 402. Prism 401 can either off-set or bend the beam path from microscope 200 so that two focusing points can be positioned closely. Mirrors 402 may be used also to bend the beam path. Further, microscope angles may be altered as illustrated.

FIG. 5 illustrates a top view of an 8-channel alignment system 500. Each microscope can be relocated along its measuring side of the field. The system comprises four sets of the image capturing units 310, 312 positioned around the imprint field 301 (staring from left-up; 310-312-310-312-310-312-310-312). As an alternative arrangement, microscopes can be arranged in a diagonally symmetric configuration (starting from left-up 312-310-310-312-312-310-310-312). Since more microscopes can be used, more alignment targets can be captured.

FIG. 10 illustrates a more detailed side view of system 500. FIG. 8A illustrates a more detailed top view of system 500 as it may be used in the iMAT system. FIG. 8B illustrates a side view of system 500 shown in FIG. 8A.

When a multiple channel imaging unit is assembled on the tool, it may be necessary to calibrate their final position. Typical accuracy of such calibration is in the range of 50 microns or less. Therefore, the accuracy in the fabrication or assembly itself would not be sufficient. This problem can be solved by using a reference template/wafer that contains grating based marks so that imaging system can read during the initial tool set up.

Referring to FIG. 6, when more than 8 channels are required, it is possible to use a beam splitter 601 and two 8-channel units 500 to compose a 16-channel unit 600. FIG. 9 illustrates a more detailed depiction of system 600 as it may be used in an iMAT system.

As already presented in a previous application (U.S. patent application Ser. No. 11/000,331), similar inclined imaging systems may be used for whole substrate imprinting processes, where the imaging unit does not block the curing UV beams. By combining both low resolution marks and high resolution moiré marks on the substrate and template, a modified microscope system may be used to capture the alignment target for whole substrate imprinting processes. Typically, low resolution alignment can provide micron-level accuracy. Such a micro level accuracy may be used also to define a “region of interest (ROI)” for the moiré pattern processing. For the systems presented herein, it may be necessary to make both the low resolution marks and moiré grating with identical pitch.

The embodiments of the present invention described above are exemplary. Many changes and modifications may be made to the disclosure recited above, while remaining within the scope of the invention. Therefore, the scope of the invention should not be limited by the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalent. 

1. An imprint lithography system operable for imprinting a pattern into a material deposited between an imprint mold and a substrate, the system comprising: a first set of imaging units positioned at a first angle relative to normal of the substrate; and a second set of imaging units positioned at a second angle relative to normal of the substrate, wherein the first and second angles are not equal to each other.
 2. The system as recited in claim 1, wherein the imaging units are operable to view alignment marks on the substrate in order to properly align the system with an imprinting field on the substrate.
 3. The system as recited in claim 2, wherein the first and second angles are defined by angles in degrees between the normal angle to the substrate and longitudinal axes of the imaging units.
 4. The system as recited in claim 3, wherein each imaging unit comprises an imaging system that emits a light beam in parallel alignment with the imaging unit's longitudinal axis towards its respective alignment mark.
 5. The system as recited in claim 1, wherein the first and second sets of imaging units each comprise four imaging units.
 6. The system as recited in claim 5, wherein the eight imaging units comprise an N-channel imaging system, wherein N≧8, further comprising: first and second N-channel imaging systems positioned at an angle to each other; and a beam splitter operable for directing imaging light beams from both N-channel imaging systems towards alignment marks on the substrate.
 7. The system as recited in claim 2, further comprising x-y actuators for re-aligning certain ones of the imaging units in order to align the system for imprinting of a portion of the imprinting field.
 8. The system as recited in claim 7, wherein the portion of the imprinting field lies along an edge of the substrate.
 9. The system as recited in claim 4, wherein certain ones of the imaging units further comprise a prism to re-direct the light beam.
 10. The system as recited in claim 4, wherein certain ones of the imaging units further comprise a mirror to re-direct the light beam. 